Did Diana Ross lend you that? Ashlee Simpson looks like an '80s diva at the Hunger Games: Catching Fire premiere in LA

The 29-year-old star and 'Fall Out Boy' singer each brought their new significant others, Meagan Camper and Evan Ross, to the family gathering held at The Coop, a party space for children.

A source told Us Weekly: 'It didn't seem awkward at all between Evan Ross and Pete Wentz. They took a family photo and were all in it -- Pete, Meagan, Ashlee and Evan.'

The source said 34-year-old Pete was first to arrive with the birthday boy with his girlfriend of two years, Meagan, and his parents in tow.

PDA alert: Ashlee Simpson and Evan Ross can't keep away from each other as they embrace on the red carpet in LA

Fancy dress: Evan and Ashlee certainly spent a lot of time putting together their outfits for their big evening out

The rocker was photographed holding hands with his new love, and shortly after Ashlee arrived with her boyfriend Evan, 25, and his mother, the legendary singer Diana Ross, along with her own mother Tina Simpson.

The friendly exes threw their son a Disney-themed party with balloons featuring famous characters from Cars, Monsters Inc. and The Incredibles.

There were reportedly 75 adults and 45 kids in attendance at the party and Ashlee's sister Jessica, who has daughter Maxwell, 18 months, and son Ace, four-months, with fiancé Eric Johnson, were photographed talking with other guests outside the venue.

'80s throwback: Ashlee Simpson and Evan Ross share their love for retro fashion as they enjoy a night out in LA

She's back: Katniss will have to compete in The Hunger Games for a second time in the movie, out November 22 in the US and November 21 in the UK